Preparation of a superconducting scandium-carbon phase

ABSTRACT

A method of preparing a superconducting body-centered cubic scandium carbide phase having the approximate composition Sc13C10 which comprises arc-melting scandium and carbon in the presence of small quantities of germanium and then annealing at temperatures above 1,000* and below 1,600* C.

United States Patent Inventors Nerses ll. Krikorian;

Angelo L. Giorgi; Eugene G. Szklarz; 7 Milton C. Kruplta, all of LosAlamos, N. Mex. Appl. No. 864,557 Filed Oct. 7, 1969 Patented Sept. 21,1971 Assignee The United States of America as represented by the UnitedStates Atomic Enem Com PREPARATION OF A SUPERCONDUCTIN G SCANDIUM-CARBONPHASE 3 Chins, 0 1 8 US. Cl. 23/208A, 252/516, 252/521 Int. Cl C0lfl7/00 Field 0! Search 23/208 A; 252/5 16, 521

[5 6] References Cited UNITED STATES PATENTS 3,482,940 12/1969 Krupka etal. 23/208 A OTHER REFERENCES Journal American Chemical Society," vol.80, pp. 4499 4503 I958) Primary Examiner-Oscar R. Vertiz AssistantExaminer-G. O. Peters Attorney-Roland A. Anderson ABSTRACT: A method ofpreparing a superconducting bodycentered cubic scandium carbide phasehaving the approximate composition Sc,;,C which comprises arc-meltingscandium and carbon in the presence of small quantities of germanium andthen annealing at temperatures above l,000 and below l,600C.

PREPARATION OF ASUPERCONDUCTING SCANDIUM- CARBON PHASE The inventiondescribed herein was made in the course of,

or under contract with the U.S. ATOMIC ENERGY COM- above l,000 C. andbelow 1,600 C. to form body-centered cubic Sc,,C Highest yields areobtained by heating at l,300 I C.-l,400 C. for 6 hours or more.Alternatively, the Sc,,C, can be prepared more rapidly by annealing for-15 minutes MISSION. 5 in the temperature interval 1,125 0.4.350" c. at-25 This invention relates to the field of superconductors. kbarspressure. In now 3,432,940, (issued Dem 9) t Annealing conditions andresults for various Sc-C-Ge compresent inventors disclose a method ofpreparing stable bodypositions are shown in the following table.

Con- Lattice parameters of Heating dltlons, b.c.c. phases Trans, lme,temperatempera- Nominal composition hours ture, C S0 0; Sc C ture, C

Ecol/568.01 21 1,300 7. 207823 8 522:1:2 7. 2 115 1, 300 7. 214:1;4 3 1,450 7. 205=l=3 SOC .nGem 16 1,300 8. 5283=h6 8. l! 105 1,100 7. 20512 8.514:1:2 8. 5

S00 Ge 1,175 7. 2056=|=4 8. 5260:l=8 7. 8 S00 GEM D1118 2 1, 370 3.5260* 8. 5 2 1, 470 8. 5263::3 8. 6 2 1, 650 No identifiable phases (0168 ,050 8. 53115: 8. 5 6 1, 370 8. 5260=h4 8. 5

80C .16 Ge .05 17 8. 0 g 'i 2: i 050 a 53025.: c 0. us

9 4 11000 No identifiable phases 8g-" :3 33g c .76 9.10 I see GM plus 19300 N0 identifiable phases 50C .87 Ge .00 17 1, 300 8. 52865.19 8. 2 $00Go .05 17 1, 300 8. 5259=|=a 7. 0 80C .o7Ge 03.--. 18 1,300 8 5276*5 8.1 ScC. Ge.tt. 18 1,300 7. 203:1:2 8 624=i=3 7.0 ScO.mGe.o 20 1,300 7.206:1:2 8 514:3 7.0 800 Ge 1a 1, 300 268:4 7. 8

1 No superconductin transition observed for measurements down to 4.0 K.

I Analyzed compost on.

centegi cubic yttrium sesquicarbide that is superconducting. They alsodisclose that a body-centered cubic lanthanum sesquicarbide normallyprepared by arc-melting is also superconducting. ln U.S. Pat.application Ser. No. 843,224 (filed July 18, I969) they further disclosethat the addition of small amounts of certain other metals to form aternary sesquicarbide produced by the method of U.S. Pat. 3,482,940significantly raises the superconducting transition temperatures forboth lanthanum and yttrium sesquicarbide. The inventors have nowdiscovered a method of preparing a body-centered cubic scandium carbidephase that isalso superconducting. This is believed to be the firstreported occurrence of superconductivity in the scandium-carbon system.

Eody -Eentered scandium carbide having the composition Sc C, can beprepared by arc-melting and annealing but exhibits no superconductingtransition down to 1 K. However, the addition of small amounts ofgermanium to the arc melt followed by annealing produces a newbodycentered cubic scandium-carbide phase having the approximatecomposition Sc,,C This latter carbide is superconducting with thetransition temperature ranging from 7.0 K. to 8.5 K.

It is therefore an object of this invention to provide a novel methodfor preparing a body-centered cubic scandium-carbide phase that issuperconducting.

Other objects and advantages of this invention willTie apparent from thefollowing description of the preferred embodiment.

The appearance of the work plus" in the table indicates that theparticular composition has been annealed at a specified 1 temperaturefor a specified time, then undergone an additional annealing for anadditional time at a different temperature as specified.

The body-centered cubic Sc,;C, phase appears to be stable 3 only over alimited temperature range. Below [000 C., it does not form, whereas itis destroyed at l,600 C. and above. However, as the data for compositionScC Ge indicate,

jthe cell can be refonned by further annealing at a lower tem- Iperature. Once formed in the matrix the phase is readily I quenched inby normal cooling techniques. Further, if the germanium content of thearc melt exceeds 0.10, the phase will not form. The fact that largevariations in germanium concen- I trations show no corresponding changein lattice parameters suggests that the germanium is not part of thestructure and the superconducting phase is a binary compound (i.e.,

What we claim is:

1. A method of preparing a superconducting body-centered cubicscandium-carbide phase comprising annealing at a temperature above l,000C., but below l,600 C., an arc melted material of nominal compositionScC Ge, where x is in the range of 002-0. 10.

2. The method of'claim l where the annealing temperature is l,300C.l,400 C. and the annealing time is 6 hours or I more.

2. The method of claim 1 where the annealing temperature is 1, 300*C.-1,400* C. and the annealing time is 6 hours or more.
 3. The method ofclaim 1 where the annealing temperature is 1, 125* C.-1,350* C., theannealing time is 5-15 minutes, and the annealing is done at 15-25 kbarspressure.